lb subcommand
The lb subcommand sets a permanent local breakpoint in the code for a specific context.
Format
lb [-p | -v] [address]
Parameters
| Item | Description |
|---|---|
| -p | Indicates that the breakpoint address is a physical or real address. |
| -v | Indicates that the breakpoint address is an effective or virtual address. |
| address | Specifies the address of the breakpoint. This can be either an effective or physical address. Symbols, hexadecimal values, or hexadecimal expressions can be used to specify the address. |
The context can either be CPU-based or thread-based. Either context is controllable through a set subcommand option. Each lb subcommand associates one context with the local breakpoint and up to eight different contexts can be set for each local breakpoint. The context is the effective address of the current thread entry in the thread table or the current processor number.
If the lb subcommand is used with no parameters, all current trace and breakpoints are displayed.
If an address is specified, the break is set with the context of the current thread or CPU. To set a break using a context other than the current thread or CPU, change the current context using the sw subcommand and the cpu subcommand.
If a local breakpoint is hit with a context that was not specified, a message is displayed, but a break does not occur.
By default, KDB kernel debugger chooses the current state of the machine. If the subcommand is entered before VMM initialization, the address is the physical address or real address. If the subcommand is entered after VMM initialization, the address is the effective or virtual address. After VMM is setup, the -p parameter must be used to set a breakpoint in real-mode for code that is not mapped V=R. Otherwise, the KDB kernel debugger expects a virtual address and translates the address.
Other
lbrk
Examples
The following is an example of how to use the lb subcommand:
KDB(0)> b execv //set break point on execv()
Assumed to be [External data]: 001F4200 execve
Ambiguous: [Ext func]
001F4200 .execve
.execve+000000 (sid:00000000) permanent & global
KDB(0)> e //exit debugger
...
Breakpoint
.execve+000000 mflr r0 <.svc_flih+00011C>
KDB(0)> ppda //print current processor data area
Per Processor Data Area [00086E40]
csa......................2FEE0000 mstack...................0037CDB0
fpowner..................00000000 curthread................E60008C0
...
KDB(0)> lb kexit //set local break point on kexit()
.kexit+000000 (sid:00000000) permanent & local < ctx: thread+0008C0 >
KDB(0)> b //display current active break points
0: .execve+000000 (sid:00000000) permanent & global
1: .kexit+000000 (sid:00000000) permanent & local < ctx: thread+0008C0 >
KDB(0)> e //exit debugger
...
Warning, breakpoint ignored (context mismatched):
.kexit+000000 mflr r0 <._exit+000020>
Breakpoint
.kexit+000000 mflr r0 <._exit+000020>
KDB(0)> ppda //print current processor data area
Per Processor Data Area [00086E40]
csa......................2FEE0000 mstack...................0037CDB0
fpowner..................00000000 curthread................E60008C0
...
KDB(0)> lc 1 thread+0008C0 //remove local break point slot 1